Growing Mediums used in Marijuana growing in a hydro set-up

By growing marijuana plants using the hydroponics system, growers have many options when it comes to the available mediums on which to allow the roots of cannabis plants to grow. The grow mediums are classified into re-usable and non-reusable. This means that some are good only for a single use while others can be used over and over again.

Re-usable grow mediums

Gravel � One of the most inexpensive, gravel is heavy and has good hold of air, there is no need to be concerned about draining because it does not hold water more than its outer layer can.
Clay � Hydroclay is the one good for hydroponics marijuana growing. This type of clay is cooked at a very high temperature to make them expand. It is very good at holding air and nutrients.
Foam � Not too many people use foam because it tends to retain water longer. It is very easy to use and can last for a long time.
Mica � This works like clay pellets but it is more expensive than expanded clay that's why not too many use it but it is also a good growing medium for hydroponics weed growing.
Pumice � This is a volcanic rock that is porous and lightweight and very good as a hydro medium.

Non-Reusable Growing Mediums

Peat Moss - This is a partially decomposed plant with lots of fiber. There are several kinds of Peat Moss like Hypnum and Reed/Sedge and they have good ph as well as rich in fiber too.
Coco Fiber � Coco coir is one of the natural hydroponics growing medium and ideal for marijuana plants in a hydro set-up. It can be used for several years and also has good ph balance.
Rockwool � Very popular among marijuana growers, rockwool is a non-degradable, porous and sterile growing medium that is ideal for root support. This is the most used growing medium because of its ample commercial availability and the benefits of its use.
Perlite � This medium can drain really fast but it tends to float when there is much water.
Vermiculite � This has excellent buffering qualities and suited for clones especially if mixed with perlite or sand.

I read somewhere that sawdust is also a good hydro growing medium for marijuana plants, is this true?

Sawdust is indeed included in the list of hydro growing mediums but it holds too much water and normally too acidic so very few actually use it.

What about sand? Can it be used as a growing medium for cannabis plants in a hydro set-up?

Yes. But it has no buffering qualities and at the same time heavy especially when wet. Some sand also has high ph so make sure to use only river sand or those coming from fresh water.